Here is some advice. In the event that you smell something...'odd'...near the kitchen sink, don't shrug your shoulders and walk away. It may or may not be the dirty cooking pot that has been sitting on the counter for a couple of days, waiting to be scrubbed. It may or may not be the disposal. If you try dumping some baking soda and orange peels down it and it doesn't help, that's a sign. If the smell gets really bad every time you open the cabinet underneath to retrieve the dish soap, that's a sign too. When you investigate your stinky cabinet that is stuffed chock-full (like top to bottom) of wadded-up plastic shopping bags, take the time to look underneath stuff.
Our garbage disposal failed in rather spectacular fashion. We just didn't know it, for about...two weeks? Maybe three? I finally figured it out last night. I removed my unforgivable stash of plastic bags that I am terribly embarrassed to admit I have, only to find a pool of water on the bottom of the cabinet. The base of our cabinet had warped into a kind of basin, even. There were small plastic odds and ends floating in it. Our saving grace was that there happened to be a medium-sized flower vase positioned directly underneath the disposal. It was full to the brim with the most foul-smelling water you could ever imagine. It literally made me gag when I dumped it out. Every time we ran water into the main compartment of the kitchen sink, water would drip,drip,drip,drip,drip from the underside of the disposal unit.
Dean ran to Home Depot to get a replacement disposal while I finished cleaning up the mess. Less than an hour later we were back in business. I had Dean cut away the 'floor' of the cabinet since it was beyond salvage anyway. It just smelled so bad, it had to go. It did seep through and soak the subfloor underneath, but thankfully it did not run underneath the whole cabinet and ruin the new kitchen flooring we *just* laid down a couple of weeks ago. Again - I think that vase totally saved us.
So, lesson learned. From now on, I will fully investigate all suspicious smells. Unless they come from Colin's rear-end.